Electrode connection



Aprl 28, 1964 M. D. STEPATH ELECTRODE CONNECTION Filed Nov. l7, 1961 Lui . 7/1//7//24 om` om m mm m 4 m {e m m A TTORNE YS.

United States Patent O 3,131,290 ELECTRODE CONNECTION Myron i). Stepath, Lancaster, Ohio, assignoto Arcair Company, Bremerton, Wash., a partnership Filed Nov. 17, 1961, Ser. No. ?153,135 4 Claims. (Cl. 219-130) This invention is related to welding or cutting apparatus in which electrodes are continuously fed toward a workpiece to be consumed in a welding or cutting operation. The electrodes are fed toward the workpiece by various hand toro-hes or automatic and semi-automatic apparatus to be consumed at the welding or cutting zone. One type of automatic unit is disclosed in United States Patent No. 2,9'89',6l7, granted June 20, 1961, which patent discloses a cutting torch which a nigid earbon electrode is fed toward a workpiece at an acourately maintained rate of movement where its leading end is consumed by an electric arc.

An object of this invention lies in the provison of a joint for successively connecting ra plurality of coppercoated carbon graphite electriodes so that a particular welding or cutting operation can be car-ried out to completion without interruption each time an eleetrode is consumed.

A further object is to provide a joint for electrodes that will not separate as it is being consumed by an electric arc.

In the attainment of these objeots, `copper-co ated caribon-gnaphte electrodes are provided with male plug and female socket terminals tor-med at their oppos-te ends eo that the plug and socket :terminals of successive electrodes may be frictionally interfitted. 'Baking into consideration the coefiicien t of friction between mating carbon-graphite surfaces, the configration of the terminals is such that a secure mechanical joint is provided between connected elect'odes that will not separate during consumption by an electric arc.

To insure adequate strength of the female terminal, the relative proportions of the terminals are such that the minimum thickness of the wall of the female terminal is at least substanti ally one sixth of the electrode diameter. This is accomplished by deriving the dimensions of the terminals as a percentage of the outside diameter of the electrode with the mating Wall s being tapered at an -angle of substantially two degrees. Radii 'at all corners of the terminals minimize the concentration of wstresses. The electrodes are -fed toward the electic arc with the female terminal as the leading end of each electrode.

Accumnlation of gases generated during eonsumption of the electrode may be prevented by the proyision of a vent hole in the side wall of the socket terminal adjacent its end wall as a further means for preventing separation of the joint during consumption.

The objects and advantages of the inventio-n will become apparent &from the following description taken in connection with the accompanying drawing in which:

FIG. 1 is a wsectional View of a portion of a c utting toroh mechanism for feeding eleotrodes toward a workpiece; and

FIG. 2 is a fragmentary view of the electrode terminals.

'FIGURE 3 is a cross sectional view taken on line 3-3 ot FIGURE 2.

With reference to FIG. 1, electnode feeding apparatus is illustrated comprising an electrode feed tube 10, an electrode seat member 12 and a drive wheel '14. Slidably received in the electrode feed tube 10 'and in driving engagement between seat member 12 and drive wheel 'lt is a partially consumed copper-ooated carbon-graphite electrode 16. The details of the :feeding apparatus form no part of the invention, but the type illustrated is that disclosed in the above referned to Patent No. 2,989,617.

&131390 Patented Apr. 28, 1964 'ice Clockwise rotation of drive wheel `14 causes the electrode 16 to be fed d-oWnwardly during a cutting operation where its leading end 17 is continuously consumed by the electric arc of the torch. Coupled to the trailing end 19 of electrode 16 is an eleotrode 18; the mating ends of the electrodes being joined by interfitting plug and socket terminals which are more clearly illwstrated in FIG. Z.

As the terminals enter the electric arc zone, they are consumed along with the electrode. Should the terminals separate before they are completely consnmed, pieces would fall onto .the 'workpiece and interfere with the cutting or wel ding operation, requiring the operation to be halted until the bits and pieces can be removed.

Connectng the electrodes is a plug terminal -Ztt formed at the trailing end 19 'of electrode 16 interfitted with a female socket terminal 22 formed at the leading end of electrode 18. At the junotion of plug 20* with end 19, the plug has a major diameter D and the surface of the plug is tapered toward its end 24 at an angle a. Socket terminal 22 has an end wall 26 and side wall 28 for friotionally receiving plug 20, the side wall 28 being tapered outwardly at an angle a toward the end 21 of the terminal 22.

To prevent cracking of the socket wall upon intention of the plug terminal therein, the minimum thickness of the wall is maintained at substantially `one-sixth of the electrode diameter. Accordingly, ieng th L and major diameter D are determined as a percentage of the outside diameter ot the electrode. Secure engagement between the interfitted terminals is obtained 'when the length L is approximately 112 percent of the diameter of the electnode 'and the major diameter D is appnoximately 66 percent ot the eleetrode diameter, the side wall being tapered at -an angle a of about two degrees. All of the corners are rounded at a radios of approximately onesixteenth of an inch to minimize stress concentration,

With the above relationshi p between the terminals and electrode diameter, the length and teper of the mat-ing surfaces provide frictional forces sufficient to prevent separation of the joint as it enters the electric arc zone. Adequate thiokness is provided at the outer end of the wall ot the female socket, the thickness of the wall always being at least one-six th of the electrode diameter, thereby reducing the possihil-ity of cracking as the terminals are joined.

Secure connection between carbon-graphite electrodes is obtained by the above described joint not obtainable heretofore, resulting in fewer stoppages and increased speed of welding and cutting Operations.

As the interfitted terminals 20' and '22 enter the heated zone, the high temperature encountered causes the gas generated by the oonsurnption of the electrode material to expand rapidly'. This rapid accum uiation and expansion of gas in the joint exets pressure tending to separate the plug from the socket. Provided in the sidewall ot the socket terminal adj acent its end wall 2.6 is a vent hole 30 which permit-s the escape of gases generated during Consumption.

As the interfitted terminals conte into contact with the heat of the electric are, the gases generated by the heat escape through vent hole 30 until the terminals are completely consumed, thereby preventing a bnildup of pressure in the joint. The diameter of vent hole 30 may be in the order of onesiX-teenth of an inc-h, although the size is not critical and is limited only by the praotieality of drilling a hole oEE less size.

With the electrodes provided with the above described plug 20 at one end and soclset 22 at the other end, they can be snccessively connected and fed continuoisly during the outting operation with the terminal 22\ always `as the leading end of each electrode. In this manner convenient lengths of electrodes can be quickly joined 

1. A JOINT FOR CONNECTING CARBON-GRAPHITE ELECTRODES COMPRISING A SOCKET TERMINAL AND A PLUG TERMINAL FRICTIONALLY RECEIVED IN SAID SOCKET TERMINAL, SAID PLUG TERMINAL HAVING A MAJOR DIAMETER SUBSTANTIALLY TWO-THIRDS OF THE ELECTRODE DIAMETER AND A LENGTH ABOUT ONE AND ONEEIGHTH TIMES THE DIAMETER OF THE ELECTRTODE, THE WALL OF SAID PLUG TERMIANAL TRAPERING FROM SAID MAJOR DIAMETER, SAID SOCKET TERMINAL HAVING AN END WALL AND A CORRESPONDINGLY TAPERED SIDE WALL FOR FRICTIONALLY RECEIVING SAID PLUG TERMINAL, THE MINIMUM THICKNESS OF SAID SIDE WALL BEING APPROXIMATELY ONE-SIXTH OF THE ELECTRODE DIAMETER, AND A VENT HOLE IN THE SIDE WALL OF SAID SOCKET TERMINAL PREVENTING THE ACCUMULATION OF GAS BETWEEN SAID TERMINALS. 